Production of polymyxins a, b, and e



United States Patent PRODUCTION OF POLYMYXINS A, B, AND E Geoffrey Clough Ainsworth, Exeter, and Clifford George Pope, London, England, assignors to Burroughs Wellcome & Co. (U. S. A.) Inc., Tuckahoe, N. Y., a corporation of New York No Drawing. Application July 30, 1951, Serial No. 239,415

Claims priority, application Great Britain December 21, 1946 7 Claims. (Cl. 195-96) This invention relates to a esses for the production, thereof.

This application is a continuation-in-part of application Serial No. 779,229, filed October 10, 1947, and based on British application Serial No. 37,619 filed December 21, 1946, now Patent No. 2,565,057.

e object of our invention is to provide a new antibiotic of good potency, especially against Gram-negative new antibiotic and to procextraction and purification myxa (Prazmowski) Migula (described in Bergeys Manfifth edition, 1939,

pages 701 to 704). ese are probably two names for the same bacillus, but if the strains are indeed different we may use either.

The strain of bacillus employed in accordance with our invention may be defined line and mucoid.

The bacillus in question is Widely distributed in nature. Besides being airborne it has been found in water, soil, milk, faeces and decaying vegetables.

According to a feature of our invention we select strains of the bacillus which during metabolism yield good amounts of the desired antibiotic. This may be done by biological assay of cultures derived from separate colonies of th culture. lt has been hate bufier and glucose.

We have obtained best results 1th an aqueous medium contalnlng 10 percent by volcharcoal.

2,695,261 Patented Nov. 23, 1954 static shallow layers or in deeper vessels with artificial aeration.

To prepare the inoculum, ture of the selected strain at is a suitable procedure.

incubation of a liquid cul- 37" C. for 18 to 24 hours An inoculum of about 5 millimillilitres of the above described nutrient medium in a fiat flask and the whole incubated at 2228 C. for 3 to 8 days. If a deep culture with artificial aeration is used, an incubation of 20-24 hours is adequate. Samples are tested for antibiotic content periodically and the culture batch harvested when the antibiotic content is substantially at a maximum.

Because the antibiotic is absorbed by filter materials, the metabolism fluid should be separated from the bacteria by centrifugation. 0.4 percent of chloroform may dded as preservative.

The metabolism fluid prepared as above described is then treated as follows (in accordance with our invention) to extract the antibiotic therefrom.

First (according to our preferred method) we make the fluid acid to a pH in this manner.

The charcoal is then filtered off and discarded.

The filtrate, containing the antibiotic, is then made neuo 8.0) by addition of alkali, such as caustic It is then treated again with a suitable activated This time (under neutral conditions) the antibiotic is absorbed.

The charcoal is filtered oif and then the antibiotic is eluted from it by washing wlth aqueous acetone, of ap- (pH 2.0 to 2.5) and/or with plain Water before the elution with 40 percent acetone.

Or instead of treating the metabolism fluid with charcoal under acid conditions the charcoal may be added under neutral conditions. The antibiotic and part of the impurities are then adsorbed together upon the charcoal,

preferred extraction method taining approximately 3.65 grams of hydrochloric acid gas dissolved in each litre. The charcoal is filtered ofl? and the filtrate is diluted immediately with four volumes of dry ether. The crude hydrochloride of the desired antibiotic then precipitates and is removed by filtration.

It may be redissolved in methanol, reprecipitated with ether, filtered oif, washed Withmore ether and dried under vacuum. 4

A further alternative in the method first above described is to recover the antibiotic from the 40 percent acetone eluate by adjusting this to pH 7 and then evaporating'ofl. the acetone under reduced pressure. The remaining solution of the antibiotic in water is stirred with activated charcoal and filtered. The filtrate is discarded. The antibiotic is eluted from the charcoal by 40 percent aqueous acetone containing approximately 2 percent by weight of sulphuric acid. The eluate is neutralised with calcium carbonate, cooled to about 4 C. and the precipitated calcium sulphate filtered off. The filtrate is frozen and dried under vacuum'while frozen, yielding the sulphate of the antibiotic.

Or after evaporation of the acetone picric acid may be add'edtoprecipitate the antibiotic as its picrate.

If it is necessary or desirable in any instance to undertake further purification of the sulphate, hydrochloride or picrate of the antibiotic produced by any of the extraction methods above described, this may be effected by conversion of the antibiotic to its helianthate. This may be done by dissolving the salt in aqueous methanol and adding a saturated solution of methyl orange. The helianthate separates'after standing at 4 C. for 12 hours.

If the quantity of methyl orange'added is such that about SOpercent of the antibiotic activity is associated with the precipitate, the latter contains the antibiotic in purified form, certain of the impurities remaining in the mother liquor in these circumstances. The precipitate may be Washed successively with water and methanol and then treated with acid in methanol to convert the antibiotic to its soluble hydrochloride or other desired acid salt, which salt may be recovered in solid form, for example by precipitation with acetone.

Alternatively the crude sulphate of the antibiotic may be converted to the hydrochloride by treatment of the former with calcium chloride, filtering off the calcium sulphate which deposits along with certain impurities.

The new antibiotic is a fairly strong base. Its hydrochloride is extremely soluble in water and less easy to handle than its less soluble sulphate. lts helianthate' is still less soluble. The base is an oil-white amorphous solid. It is stable for short periods in aqueous solution at a pH of 3 to 8. It is very unstable in alkaline solutions. It cannot be extracted from aqueous solution by chloroform. It is most conveniently dissolved in water or methanol. The new antibiotic is a polypeptide yielding on hydrolysis d-leucine, epsilon methyl octanoic acid, l-threonine as the sole hydroxy amino acid, and in excess of 40 percent alpha-gamma-diaminobutwic acid as the sole basic amino acid constituent calculated as g. amino acid g. polymyxin base further characterized by the absence of dicarboxylic amino acids from the hydrolysate.

The antibiotic has been proved by in vivo experiments to have chemotherapeutic activity and give a useful degree of protection against the following pathogenic organenreritides, Sal. para typhi, Sal. pullorum, Sh. flexner, Sh.

schmitz, Sh. shiga, Sh. gallinarum, Sh. sonnet and Pyocyaneus sepsis. Culture specimens-of the three polymyxins identified in this application are on file at the Agricultural Research Service of the United States Department of Agriculture, Peoria 5, Illinois, marked with the U. S. D. A. Type Collection numbers- Polymy-xin ANRRL B-1550 Polymyxin B-NRRL 13-1551 Polymyxin ENRRL 3-1552 We claim:

1. A process of preparing polymyxins A, B andE and mixtures thereof which comprises culturing a species of Baccilus polymyxa of the type selected from the class consisting of a species yielding polymyxin A, polymyxin E and mixtures thereof trient medium containing glucose and a phosphate buffer and harvesting the product.

2. Process specified in claim 1 wherein culture takes place in a proteinaceous nutrient medium containing 3 percent glucose, 0.002 percent manganous sulphate and 0.6 per cent diammonium hydrogen sulphate.

3. The process for producing polymyxins A, 'B' and E and mixtures thereof which comprises cultivating a species of bacteria of the type B. polymyxa in an aqueous-medium comprising a proteinaceous material and in the presenceof an assimilable carbon source and a phosphate material.

4. A process of preparing polymyxins A, B and E-andmixtures thereof which comprises culturing a species of Bacillus polymyxa of the type selected from the class consisting of a species yielding polymyxin A, p'olymyxin B, polymyxin E and mixtures thereof in a proteinaceous medium containing an assimilable carbon source and a phosphate buffer and harvesting the product.

5. A process of preparing polymyxins A, B and E and mixtures thereof which comprises incubating a liquid culture of a species of Bacillus polymyxa of the type selected from the class consisting of a species yielding polymyxin A, polymyxin B, polymyxin E and mixtures thereof at a moderate temperature of from about 18 to 24 hours, adding an inoculum of the resulting culture toaproteinaceous nutrient medium and incubating the mixture for a period of from 3 to 8 days and harvesting the antibiotic product.

6. The process of claim 5 wherein the inoculated nutrient medium is cultured with artificial aeration for a period of from 20 to 24 hours.

7. The process of claim 5 wherein incubation of the inoculated nutrient medium is carried out at a temperature of from about 22 to 28 C.

References Cited in the file of thispatent UNITED STATES PATENTS OTHER REFERENCES Tilden et al.: Jour. Bact. 43, 1942, pages 527 to 544. Stansley et al.: Bulletin Johns Hopkins Hospital, July 1947, pages 43 to 54.

Stansley: The polymyxins, I. A. M. A. 7, December 1949, pages 807-818.

I ones, T. S. 6.: Chemical Evidence for the Multiplicity of the Antibiotics Produced by Bacillus Polymyxa, Ann: N. Y. Acad. Sci., 51:909, 1949.

Benedict and Stodola: Annals of the New York Academy of Sciences, vol. 51, page 866. 

1. A PROCESS OF PREPARING POLYMYXINS A, B AND E AND MIXTURES THEREOF WHICH COMPRISES CULTURING A SPECIES OF BACCILUS POLYMYXA OF THE TYPE SELECTED FROM THE CLASS CONSISTING OF A SPECIES YIELDING POLYMYXIN A, POLYMYXIN B, POLYMYXIN E AND MIXTURES THEREOF IN A PROTEINACEOUS NUTRIENT MEDIUM CONTAINING GLUCOSE AND PHOSPHATE BUFFER AND HARVESTING THE PRODUCT. 